余弦函数的对称轴是π,3π,.,2kπ+π
正弦函数的对称轴是π/2,5π/2,.,2kπ+π/2
f(x)=cos^2(x+π/12)=(1/2)cos(2x+π/6)+1/2
f(x0)=(1/2)cos(2x0+π/6)+1/2
则对称轴为2x0+π/6=2kπ+π